1. Technical Background
This application is a National Phase filing under 35 U.S.C. 371 of International Application No. PCT/US98/24305, filed Nov. 13, 1998, based upon Netherlands Application No. 1007584 filed Nov. 19, 1997.
The present invention relates to a vascular filter which can be temporarily placed inside a blood vessel for the purpose of intercepting thrombus.
2. Discussion
Some basic types of vascular filters are generally known, wherein a single filter element or member extends substantially transverse to the direction of flow inside the blood vessel, and is wedged against the blood vessel wall due to the fact that it has a dimension slightly larger than the inside diameter of the blood vessel. Vascular filters may often be used in the vena cava, and may be described in such event as a xe2x80x9cvena cava filter.xe2x80x9d
Known vascular filters may have some disadvantages, some of which may relate to their reliability. As such, known vascular filters may consist of a network of interconnected ribs, which extend substantially in a radial direction in relation to the blood vessel. Unfortunately, the entire filter may shift position if one of the ribs breaks. In addition, the free ends of the ribs, which are positioned under a certain pressure against the internal wall of the blood vessel, may cause trauma to the vessel wall, or may become embedded in it which may involve risk for the patient.
Another disadvantage of known vascular filters may be a possibility of shifting position in the blood flow inside the blood vessel, even when the filter maintains its proper shape, if a known vascular filter may have been incorrectly placed in a portion of the blood vessel which is too wide. In such an event, a vascular filter may not grab sufficient hold on the internal wall of the blood vessel.
Accordingly, an object of the present invention is to provide a vascular filter for delivery through a catheter in a compressed shape, where it tends to resiliently expand within the blood vessel. The vascular filter tends to trap thrombus or particles, and resist their movement further downstream. The filter includes, in a position of use, a circumference corresponding to the internal diameter of the blood vessel transverse to the longitudinal direction hereof.
With a vascular filter according to the present invention, the tubular section tends to wedge itself in place within the blood vessel, exerting pressure locally, along a large section of contact area, on the wall of the blood vessel. Accordingly, the filter tends to exert pressure on the internal wall of the blood vessel which could result in perforation of the blood vessel, but tends to hold itself in place. The vascular filter will consequently tend not to shift position.
In addition, the vascular filter according to the present invention cannot rotate transversely or tilt over, which is another important advantage of the present invention. In a preferred embodiment, a vascular filter according to the present invention has preferably been formed out of one single piece, which provides advantages, including simplicity.
In another preferred embodiment, a vascular filter according to the present invention includes a first and second filter section, arranged on either side of a body member. The body member and the filter sections thus enclose a space. Due to the elongated shape of the vascular filter according to the present invention, and the arranging of the first and second section on either side of the body member, the present filter has an enhanced filtering effect. In other words, two opportunities have been created for intercepting thrombus moving inside the blood vessel. The position of the filter inside the vena cava or another the blood vessel is therefore not dependent on the route along which it has been introduced, as a result of which the physician concerned has more freedom when choosing a route for introducing the vascular filter.
Another embodiment of the vena cava filter according to the present invention incorporates the feature that, when seen in an axial direction, the passage has the shape of a regular polygon, and provides several smaller filtering xe2x80x9ccellsxe2x80x9d. The purpose of these filtering cells is to intercept thrombus moving inside the blood vessel.
The filter sections, as arranged according to an embodiment described above on either side of the tubular body section, are preferably identical in shape, thereby enhancing the simplicity of the vascular filter according to the present invention.
A vascular filter may have been made of a braiding of wire-like elements, or a single plate-like element having a series of cuts at places corresponding to the positions of passages, or a tubular element also having a series of cuts at places corresponding to the positions of passages. It is thus preferably possible to effect under the influence of heat at least deformation of the material and possibly expansion of the vascular filter, which may be made in one of three ways mentioned, to obtain the ultimate shape and in particular the circumference hereof. Possible junctions are preferably effected by melting or welding free ends together, or by employing such a cutting pattern that the basic shape of the vascular filter according to the present invention is obtained. In addition, an advantage of the filter made of a tubular body is that it can be reduced to the dimensions of the tubular body, which dimensions may be very small, so that also the dimensions of the catheter required to introduce the filter may be very small.
It should be noted that the present invention also relates to methods for manufacturing vascular filters as described herein.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.
The invention will be explained in greater detail below with reference to the attached drawings of a number of examples of embodiments hereof.